Vinyl chloride polymers plasticized with mercaptobenzothiazoles



2,762,786 Patented Sept. 11, 1956- VINYL CHLORIDE POLYIVIERS PLASTICIZED WITH MERCAPTOBENZOTHIAZOLES Joachim Dazzi, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application June 23, 1950, Serial No. 170,049, now Patent No. 2,695,299, dated November 23, 1954. Divided and this application July 19, 1954, Serial No. 444,374

5 Claims. (Cl. 260-30.2)

The present invention relates to new derivatives of 2- mercaptobenzothiazole and to methods of preparing the same.

The invention provides products having the general formula (ILIS(OH2CH2O)OCR \s/ in which n is an integer of from 1 to 30 and R is a member of the group consisting of hydrogen and saturated hydrocarbon residues of from 1 to 29 carbon atoms. One class of compounds having the above general formula includes members having the general structure \s/ in which R is a member of the group consisting of hydrogen and saturated hydrocarbon residues of from 1 to 29 carbon atoms. This class of compounds includes esters of saturated, hydrocarbon monocarboxylic acids of from 1 to 30 carbon atoms and 2(2-benzothiazylmercapto)- ethanol. The latter compound is readily obtainable by reaction of one mole of Z-mercaptobenzothiazole with one mole of ethylene oxide, ethylene glycol or ethylene chlorohydrin.

Another class of compounds includes esters of the saturated, hydrocarbon monocarboxylic acids and products obtainable by reaction of one mole of mercaptobenzothiazole with more than one mole of ethylene X- ide. This class has the general formula in which n is an integer of from 1 to 29 and R is as herein defined. Condensation products of one mole of 2-mercaptobenzothiazole with from 5 to 30 moles of ethylene oxide are described in the Gluesenkamp U. S. Patent No. 2,498,617, which is assigned to the same assignee as is the present case.

Accordingly, the present invention relates generally to esters of saturated, hydrocarbon monocarboxylic compounds of from 1 to 30 carbon atoms and a member of the group consisting of 2-(2-benzothiazylmercapto)ethanol and polyglycols obtained by reacting mercaptobenzothiazole with more than one mole of ethylene oxide, such esters being obtained substantially according to the scheme in which n is an integer of from 1 to 30, R is a hydrocarbon residue of from 1 to 29 carbon atoms and X is a member of the group consisting of hydroxy, OCOR, chlorine and bromine. As carboxylic components there may be employed, for example, such aliphatic carboxy compounds as formic acid, acetyl bromide, acetic anhydride, propionyl, chloride, butyric anhydride, valeric acid, 2-ethylhexoic acid, lauroyl chloride, myristoyl bromide, behenic acid, cerotic acid and melissic acid; such aromatic compounds as benzoyl chloride, E-biphenyl carboxylic acid and Z-naphtoic acid; such alicyclic compounds as cyclohexanecarboxylic acid and Z-methylcyclohexanecarboxylic acid; and such aralkyl compounds as 2-toluic acid, a toluic acid, and hydrocinnamic acid.

Esterification of benzothiazylmercaptoethanol or of the higher ratio mercaptobenzothiazole-ethylene oxide condensation products with the above carboxylic compounds takes place readily at ordinary, increased or decreased temperatures depending upon the nature of the reactants, When using the free acids, some esterification occurs upon contacting the two reactants at ordinary temperatures, but optimum yields of the present esters are obtained by heating a mixture of the mercapto compound and the acid, preferably at refluxing temperature and in the presence of an esterifying catalyst. As esterifying catalysts suitable for the present purpose may be mentioned acidic or basic materials such as sulfuric acid, phosphoric acid, p-toluenesulfonic acid, sodium methoxide, etc.

When working with acid halides optimum yields are obtained when operating at decreased temperatures, i. e., at temperatures of, say, from minus 10 C. to 10 C. With these highly reactive esterifying agents, the use of a catalyst is unnecessary and often detrimental to smooth condensation.

Inasmuch as the esterification reaction involves the condensation of one mole of the hydroxy thiazole compound with one mole of the acid, stoichiometric proportions of the reactants are advantageusly employed. However, since any excess of either the hydroxy compound or the acid may be readily recovered from the final prodnet, the quantity of reactants employed in the initial reac tion is immaterial. It is preferred, however, to use an excess of the acid compound in order to minimize incomplete esterification.

The present products are stable, somewhat high-boiling materials which range from viscous liquids to waxy or crystalline solids. They may be employed for a variety of technical uses, i. e., as plasticizers for synthetic resins and plastics, and as intermediates in the production of moisture-proofing agents, biological toxicants, surfaceactive agents, etc.

Advantageously employed as plasticizers, particularly for vinyl chloride polymers, i. e., polyvinyl chloride and copolymers of vinyl chloride with unsaturated monomers, are esters having the general structure in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms. As examples of compounds having the above general formula and especially valuable as plasticizers for vinyl chloride polymers may be mentioned the 2-(benzothiazylmercapto)ethyl esters of valeric acid, n-hexoic acid, pelargonic acid, lauric acid, 2-naphthoic acid, hydrocinnamic acid and cyclohexanecarboxylic acid and the esters of these acids with 2-mercaptobenzothiazole-ethylene oxide condensation products in which the molar ratio of mercapto compound to ethylene oxide is 1:2 and 1:3.

I have found that esters of 2-(benzothiazylmercapto)- ethanol or .of 2-mercaptobenzothiazole-ethylene oxide condensation products having the formula shown above are of outstanding value as plasticizers for polyvinyl chloride and for copolymers of at least 70 per cent by weight of vinyl chloride and up to 30 per cent by weight of an unsaturated monomer copolymerized therewith, for example vinyl acetate, vinylidene chloride, etc. These esters not only soften vinyl chloride polymers but also impart a high degree of low temperature flexibility, very good temperature stability and great mechanical strength to these polymers. They are compatible with vinyl chloride polymers and show no exudation of plasticizer even at plasticizer content of up to 50 per cent. Although the quantity of plasticizer will depend upon the particular polymer to be plasticized and upon its molecular weight, it is generally found that compositions having from 5 per cent to 50 per cent by weight of plasticizer will, in most cases, be satisfactory for general utility. The good flexibility of the plasticized compositions increases with increasing plasticizer concentration.

In evaluating plasticizer efliciency use is made of the following empirical .testing procedures:

Compatibility-Visual inspection of the plasticized composition is employed, incompatibility of the plasticizer with the polymer being demonstrated by cloudiness and exudation of the plasticizer.

Low temperature flexibiliry.Low temperature flexibility is one of the most important properties of elastomeric vinyl compositions. While many plasticizers will produce flexible compositions at room temperature the flexibility of these compositions at low temperatures may vary considerably, i. e., plasticized polyvinyl chloride compositions that are flexible at room temperature often become very brittle and useless at low temperatures. Low temperature flexibility tests herein employed are according to the Clash'Berg method. This method determines the torsional flexibility of a plastic at various temperatures. The temperature at which the vinyl composition exhibits an arbitrarily established minimum flexibility is defined as the Low Temperature Flexibility of the composition. This value may also be defined as the lower temperature limit of the plasticized compositions usefulness as an elastomer.

Water resistance-The amount of leaching that takes place when the plasticized composition is immersed in distilled water for 24 hours is determined.

The invention is further illustrated, but not limited, by the following examples:

Example 1 To a solution of 211.4 g. (1 mole) of 2-(2-benzothiazylmercapto)ethanol (prepared by the reaction of mercaptobenzothiazole with ethylene chlorohydrin) in an excess of toluene there was added 173 g. (1.2 moles) of Z-ethylhexoic acid and 5 g. of .p-toluenesulfonicacid as a catalyst. The resulting mixture was then refluxed for a time of 8 hours, during which time water was removed from the reaction Zone as it was formed. Removal of the solvent and excess Z-ethylhexoic acid from the resulting reaction product gave substantially pure 2-(2-benzothiazylmercapto)ethyl 2-ethylhexoate, B. P. 201 C. to 208 C./0.7 mm. of mercury.

Example 2 To a solution of 110.6 g. (0.5 mole) of 2-(2-benzothiazylmercapto) ethanol (prepared by reaction of benzothiazole with ethylene oxide in 245.4 g. of xylene) there was added 33.9 g. of dry pyridine and 50 ml. of ether. The resulting mixture was then cooled to a temperature of minus 5 C. to 0 C. and during a period of 42 minutes there was added to the cooled mixture 85.5 g. (0.525 mole) of Z-ethylhexoyl chloride. The whole was then stirred for 3.5 hours at a temperature of from minus 2 C. to 3 C., diluted with water, and washed neutral. Removal of the solvents by distillation at up to 100 C./1 mm. pressure yielded 128 g. of crude 2-(2-benzothiazylmercapto)ethyl 2-ethylhexoate, n =1.5608. Since the crude product was found to have an acid value of 9.67 per cent (indicating the presence of unreacted acid) it was again submitted to esterification by refluxing it for a period of 3 hours with 0.5 mole of 2-ethylhexoic acid in the presence of a small amount of p-toluenesulfonic acid as esterifying catalyst and an excess of toluene as diluent. During this time 1.5 ml. of water was collected, showing further esterification. At the end of that time the product was fractionally distilled to yield the substantially pure 2-(2-benzothiazylmercapto)ethyl 2- ethylhexoate, B. P. 200 C. to 210 C. at 0.7 mm., n =1.5625.

Example 3 Into a 250 ml. three-necked flask fitted with an agitator, thermometer and dropping funnel was placed 90 g. (0.1 mole) of a 23.5 per cent solution of 2-(2-benzothiazylmercapto)ethanol in p-xylene and 9 g. (0.11 mole) of pyridine. The mixture was cooled in a salt-ice bath while 24.7 g. (0.1 mole) of myristoyl chloride was added over a period of one hour. The flask contents were stirred an additional hour while in the ice bath and then for another minutes at room temperature. The reaction mixture was washed two times with water, once with a dilute sodium bicarbonate solution, three more times with water, dried over calcium chloride, filtered and distilled underreduced pressure to a pot temperature of 80 C./ 3 mm. There was thus obtained 39 g. of 2-(2-benzothiazylmercapto)ethyl myristate as residue.

Proceeding substantially as in the above examples 2-(2-benzothiazylmercapto)ethanol may be similarly reacted with other saturated, unsubstituted monocarboxylic acids of from 1 to 30 carbon atoms. Thus, instead of the carboxylic acids employed in the above examples there may be used, c. g., acetic acid, butyric acid, n-caproic acid, capric acid, stearic acid, cyclohexanecarboxylic acid, a-toluic acid, benzoic acid, 4-phenylbenzoic acid, etc. to yield the 2-(2-benzothiazylmercapto)ethyl esters thereof. Also, instead of 2-(2-benzothiazylmercapto)ethanol there may be employed reaction products of one mole of 2- mercaptobenzothiazole with more than one mole of ethylene oxide, i. e., condensation products prepared from one mole of 2-mercaptobenzothiazole and from 2 to 30 moles of ethylene oxide.

Example 4 Sixty parts of polyvinyl chloride and 40 parts by weight of the 2-(Z-benzothiazylmercapto)ethyl 2-ethylhexoate, B. P. 200 to 210 C. of Example 2 are mixed on a rolling mill to a homogeneous blend. During the milling there was observed substantially no fuming and discoloration.

A molded sheet of the mixture was clear and transparent and substantially colorless. Testing of the molded sheet for low temperature flexibility, according to the testing procedure described above, gave a value of minus 26 C., which value denotes extremely good low temperature properties. Tests of the water-resistance properties of the plasticized material employing the test procedure described above showed a solids-loss of only 0.2 per cent.

Instead of the 2-(2-benzothiazylmercapto) ethyl 2-ethylhexoate employed in the above example there may be advantageously employed as plasticizers for polyvinyl chloride and for copolymers of vinyl chloride other esters having the general structure in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms, e. g., the 2- (benzothiazylmercapto)ethyl esters of butyric acid, capric acid, lauric acid, 4-toluic acid, hydrocinnamic acid or cyclohexanecarboxylic acid. Also, instead of using the Z-(benzothiazylmercapto)ethyl esters of these acids there may be employed esters of the above acids and the condensation products of one mole of Z-mercaptobenzothiazole with from 2 to 3 moles of ethylene oxide,

While the above example particularly illustrates compositions in which the ratio of plasticizer to polymer content is 40:60, this ratio being employed in order to get comparable efiiciencies, the content of ester to polyvinyl chloride may be widely varied, depending upon the properties desired in the final product. For many purposes a plasticizer content of, say, from only per cent to 20 per cent is preferred. The above esters are com patible with polyvinyl chloride over wide ranges of concentrations, up to 50 per cent of esters based on the total weight of the plasticized composition yielding desirable products.

Although the invention has been described particularly with reference to the use of the present esters as plasticizers for polyvinyl chloride, these esters are advantageously employed also as plasticizers for copolymers of vinyl chloride, for example the copolymers of vinyl chloride with vinyl acetate or vinylidene chloride, etc. Preferably such copolymers have a high vinyl chloride content, i. e., a vinyl chloride content of at least 70 per cent by weight of vinyl chloride and up to 30 per cent by weight of the copolymerizable monomer.

The plasticized polyvinyl halide compositions of the present invention have good thermal stability; however, for many purposes it may be advantageous to use known stabilizers in the plasticized compositions. The esters are of general utility in softening vinyl chloride polymers. They may be used as the only plasticizing component in a compounded vinyl chloride polymer or they may be used in conjunction with other plasticizers.

This application is a division of my copending application Serial No. 170,049 filed June 23, 1950, now Patent No. 2,695,299.

S(CH2CH20)r-OCR in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms.

2. A resinous composition comprising polyvinyl chloride plasticized with an ester having the general formula i-s (CH7CHIO)1|O on in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms.

3. A resinous composition comprising a copolymer of at least percent by weight of vinyl chloride and up to 30 per cent by weight of an unsaturated monomer copolymerizable therewith, said copolymer being plasticized with an ester having the general formula CS(CH2CH70)O0R \S/ in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms.

4. A resinous composition comprising a copolymer of at least 70 per cent by weight of vinyl chloride and up to 30 per cent by weight of an unsaturated monomer copolymerizable therewith, said copolymer being plasticized with an ester having the general formula in which n is an integer of from 1 to 3 and R is a member of the group consisting of alkyl, aryl, aralkyl and cycloalkyl radicals of from 4 to 12 carbon atoms, said ester being from 5 to 50 per cent of the weight of the composition.

5. A resinous composition comprising polyvinyl chloride plasticized with 2-(2-benzothiazylmercapto)ethyl 2- ethylhexoate.

No references cited. 

1. A RESINOUS COMPOSITION COMPRISING A POLYMERIC MATERIAL SELECTED FROM THE CLASS CONSISTING OF POLYVINYL CHLORIDE AND A COPLYMER OF AT LEAST 70% BY WEIGHT OF VINYL CHLORIDE AND UP TO 30% BY WEIGHT OF AN UNSATURATED MONOMER COPOLYMERIZABLE THEREWITH, SAID POLYMERIC MATERIAL BEING PLASTICIZED WITH AN ESTER HAVING GENERAL FORMULA. 